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Date:   Wed, 12 Aug 2020 11:25:15 +0200
From:   Ulf Hansson <ulf.hansson@...aro.org>
To:     "Rafael J. Wysocki" <rjw@...ysocki.net>
Cc:     Linux PM <linux-pm@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Alan Stern <stern@...land.harvard.edu>,
        Wolfram Sang <wsa@...nel.org>,
        Sakari Ailus <sakari.ailus@...ux.intel.com>
Subject: Re: [PATCH] PM: runtime: Add kerneldoc comments to multiple helpers

On Fri, 31 Jul 2020 at 19:03, Rafael J. Wysocki <rjw@...ysocki.net> wrote:
>
> From: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
>
> Add kerneldoc comments to multiple PM-runtime helper functions
> defined as static inline wrappers around lower-level routines to
> provide quick reference decumentation of their behavior.
>
> Some of them are similar to each other with subtle differences only
> and the behavior of some of them may appear as counter-intuitive, so
> clarify all that to avoid confusion.
>
> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>

Reviewed-by: Ulf Hansson <ulf.hansson@...aro.org>

Kind regards
Uffe

> ---
>  include/linux/pm_runtime.h |  246 +++++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 246 insertions(+)
>
> Index: linux-pm/include/linux/pm_runtime.h
> ===================================================================
> --- linux-pm.orig/include/linux/pm_runtime.h
> +++ linux-pm/include/linux/pm_runtime.h
> @@ -60,58 +60,151 @@ extern void pm_runtime_put_suppliers(str
>  extern void pm_runtime_new_link(struct device *dev);
>  extern void pm_runtime_drop_link(struct device *dev);
>
> +/**
> + * pm_runtime_get_if_in_use - Conditionally bump up runtime PM usage counter.
> + * @dev: Target device.
> + *
> + * Increment the runtime PM usage counter of @dev if its runtime PM status is
> + * %RPM_ACTIVE and its runtime PM usage counter is greater than 0.
> + */
>  static inline int pm_runtime_get_if_in_use(struct device *dev)
>  {
>         return pm_runtime_get_if_active(dev, false);
>  }
>
> +/**
> + * pm_suspend_ignore_children - Set runtime PM behavior regarding children.
> + * @dev: Target device.
> + * @enable: Whether or not to ignore possible dependencies on children.
> + *
> + * The dependencies of @dev on its children will not be taken into account by
> + * the runtime PM framework going forward if @enable is %true, or they will
> + * be taken into account otherwise.
> + */
>  static inline void pm_suspend_ignore_children(struct device *dev, bool enable)
>  {
>         dev->power.ignore_children = enable;
>  }
>
> +/**
> + * pm_runtime_get_noresume - Bump up runtime PM usage counter of a device.
> + * @dev: Target device.
> + */
>  static inline void pm_runtime_get_noresume(struct device *dev)
>  {
>         atomic_inc(&dev->power.usage_count);
>  }
>
> +/**
> + * pm_runtime_put_noidle - Drop runtime PM usage counter of a device.
> + * @dev: Target device.
> + *
> + * Decrement the runtime PM usage counter of @dev unless it is 0 already.
> + */
>  static inline void pm_runtime_put_noidle(struct device *dev)
>  {
>         atomic_add_unless(&dev->power.usage_count, -1, 0);
>  }
>
> +/**
> + * pm_runtime_suspended - Check whether or not a device is runtime-suspended.
> + * @dev: Target device.
> + *
> + * Return %true if runtime PM is enabled for @dev and its runtime PM status is
> + * %RPM_SUSPENDED, or %false otherwise.
> + *
> + * Note that the return value of this function can only be trusted if it is
> + * called under the runtime PM lock of @dev or under conditions in which
> + * runtime PM cannot be either disabled or enabled for @dev and its runtime PM
> + * status cannot change.
> + */
>  static inline bool pm_runtime_suspended(struct device *dev)
>  {
>         return dev->power.runtime_status == RPM_SUSPENDED
>                 && !dev->power.disable_depth;
>  }
>
> +/**
> + * pm_runtime_active - Check whether or not a device is runtime-active.
> + * @dev: Target device.
> + *
> + * Return %true if runtime PM is enabled for @dev and its runtime PM status is
> + * %RPM_ACTIVE, or %false otherwise.
> + *
> + * Note that the return value of this function can only be trusted if it is
> + * called under the runtime PM lock of @dev or under conditions in which
> + * runtime PM cannot be either disabled or enabled for @dev and its runtime PM
> + * status cannot change.
> + */
>  static inline bool pm_runtime_active(struct device *dev)
>  {
>         return dev->power.runtime_status == RPM_ACTIVE
>                 || dev->power.disable_depth;
>  }
>
> +/**
> + * pm_runtime_status_suspended - Check if runtime PM status is "suspended".
> + * @dev: Target device.
> + *
> + * Return %true if the runtime PM status of @dev is %RPM_SUSPENDED, or %false
> + * otherwise, regardless of whether or not runtime PM has been enabled for @dev.
> + *
> + * Note that the return value of this function can only be trusted if it is
> + * called under the runtime PM lock of @dev or under conditions in which the
> + * runtime PM status of @dev cannot change.
> + */
>  static inline bool pm_runtime_status_suspended(struct device *dev)
>  {
>         return dev->power.runtime_status == RPM_SUSPENDED;
>  }
>
> +/**
> + * pm_runtime_enabled - Check if runtime PM is enabled.
> + * @dev: Target device.
> + *
> + * Return %true if runtime PM is enabled for @dev or %false otherwise.
> + *
> + * Note that the return value of this function can only be trusted if it is
> + * called under the runtime PM lock of @dev or under conditions in which
> + * runtime PM cannot be either disabled or enabled for @dev.
> + */
>  static inline bool pm_runtime_enabled(struct device *dev)
>  {
>         return !dev->power.disable_depth;
>  }
>
> +/**
> + * pm_runtime_has_no_callbacks - Check if runtime PM callbacks may be present.
> + * @dev: Target device.
> + *
> + * Return %true if @dev is a special device without runtime PM callbacks or
> + * %false otherwise.
> + */
>  static inline bool pm_runtime_has_no_callbacks(struct device *dev)
>  {
>         return dev->power.no_callbacks;
>  }
>
> +/**
> + * pm_runtime_mark_last_busy - Update the last access time of a device.
> + * @dev: Target device.
> + *
> + * Update the last access time of @dev used by the runtime PM autosuspend
> + * mechanism to the current time as returned by ktime_get_mono_fast_ns().
> + */
>  static inline void pm_runtime_mark_last_busy(struct device *dev)
>  {
>         WRITE_ONCE(dev->power.last_busy, ktime_get_mono_fast_ns());
>  }
>
> +/**
> + * pm_runtime_is_irq_safe - Check if runtime PM can work in interrupt context.
> + * @dev: Target device.
> + *
> + * Return %true if @dev has been marked as an "IRQ-safe" device (with respect
> + * to runtime PM), in which case its runtime PM callabcks can be expected to
> + * work correctly when invoked from interrupt handlers.
> + */
>  static inline bool pm_runtime_is_irq_safe(struct device *dev)
>  {
>         return dev->power.irq_safe;
> @@ -191,97 +284,250 @@ static inline void pm_runtime_drop_link(
>
>  #endif /* !CONFIG_PM */
>
> +/**
> + * pm_runtime_idle - Conditionally set up autosuspend of a device or suspend it.
> + * @dev: Target device.
> + *
> + * Invoke the "idle check" callback of @dev and, depending on its return value,
> + * set up autosuspend of @dev or suspend it (depending on whether or not
> + * autosuspend has been enabled for it).
> + */
>  static inline int pm_runtime_idle(struct device *dev)
>  {
>         return __pm_runtime_idle(dev, 0);
>  }
>
> +/**
> + * pm_runtime_suspend - Suspend a device synchronously.
> + * @dev: Target device.
> + */
>  static inline int pm_runtime_suspend(struct device *dev)
>  {
>         return __pm_runtime_suspend(dev, 0);
>  }
>
> +/**
> + * pm_runtime_autosuspend - Set up autosuspend of a device or suspend it.
> + * @dev: Target device.
> + *
> + * Set up autosuspend of @dev or suspend it (depending on whether or not
> + * autosuspend is enabled for it) without engaging its "idle check" callback.
> + */
>  static inline int pm_runtime_autosuspend(struct device *dev)
>  {
>         return __pm_runtime_suspend(dev, RPM_AUTO);
>  }
>
> +/**
> + * pm_runtime_resume - Resume a device synchronously.
> + * @dev: Target device.
> + */
>  static inline int pm_runtime_resume(struct device *dev)
>  {
>         return __pm_runtime_resume(dev, 0);
>  }
>
> +/**
> + * pm_request_idle - Queue up "idle check" execution for a device.
> + * @dev: Target device.
> + *
> + * Queue up a work item to run an equivalent of pm_runtime_idle() for @dev
> + * asynchronously.
> + */
>  static inline int pm_request_idle(struct device *dev)
>  {
>         return __pm_runtime_idle(dev, RPM_ASYNC);
>  }
>
> +/**
> + * pm_request_resume - Queue up runtime-resume of a device.
> + * @dev: Target device.
> + */
>  static inline int pm_request_resume(struct device *dev)
>  {
>         return __pm_runtime_resume(dev, RPM_ASYNC);
>  }
>
> +/**
> + * pm_request_autosuspend - Queue up autosuspend of a device.
> + * @dev: Target device.
> + *
> + * Queue up a work item to run an equivalent pm_runtime_autosuspend() for @dev
> + * asynchronously.
> + */
>  static inline int pm_request_autosuspend(struct device *dev)
>  {
>         return __pm_runtime_suspend(dev, RPM_ASYNC | RPM_AUTO);
>  }
>
> +/**
> + * pm_runtime_get - Bump up usage counter and queue up resume of a device.
> + * @dev: Target device.
> + *
> + * Bump up the runtime PM usage counter of @dev and queue up a work item to
> + * carry out runtime-resume of it.
> + */
>  static inline int pm_runtime_get(struct device *dev)
>  {
>         return __pm_runtime_resume(dev, RPM_GET_PUT | RPM_ASYNC);
>  }
>
> +/**
> + * pm_runtime_get_sync - Bump up usage counter of a device and resume it.
> + * @dev: Target device.
> + *
> + * Bump up the runtime PM usage counter of @dev and carry out runtime-resume of
> + * it synchronously.
> + *
> + * The possible return values of this function are the same as for
> + * pm_runtime_resume() and the runtime PM usage counter of @dev remains
> + * incremented in all cases, even if it returns an error code.
> + */
>  static inline int pm_runtime_get_sync(struct device *dev)
>  {
>         return __pm_runtime_resume(dev, RPM_GET_PUT);
>  }
>
> +/**
> + * pm_runtime_put - Drop device usage counter and queue up "idle check" if 0.
> + * @dev: Target device.
> + *
> + * Decrement the runtime PM usage counter of @dev and if it turns out to be
> + * equal to 0, queue up a work item for @dev like in pm_request_idle().
> + */
>  static inline int pm_runtime_put(struct device *dev)
>  {
>         return __pm_runtime_idle(dev, RPM_GET_PUT | RPM_ASYNC);
>  }
>
> +/**
> + * pm_runtime_put_autosuspend - Drop device usage counter and queue autosuspend if 0.
> + * @dev: Target device.
> + *
> + * Decrement the runtime PM usage counter of @dev and if it turns out to be
> + * equal to 0, queue up a work item for @dev like in pm_request_autosuspend().
> + */
>  static inline int pm_runtime_put_autosuspend(struct device *dev)
>  {
>         return __pm_runtime_suspend(dev,
>             RPM_GET_PUT | RPM_ASYNC | RPM_AUTO);
>  }
>
> +/**
> + * pm_runtime_put_sync - Drop device usage counter and run "idle check" if 0.
> + * @dev: Target device.
> + *
> + * Decrement the runtime PM usage counter of @dev and if it turns out to be
> + * equal to 0, invoke the "idle check" callback of @dev and, depending on its
> + * return value, set up autosuspend of @dev or suspend it (depending on whether
> + * or not autosuspend has been enabled for it).
> + *
> + * The possible return values of this function are the same as for
> + * pm_runtime_idle() and the runtime PM usage counter of @dev remains
> + * decremented in all cases, even if it returns an error code.
> + */
>  static inline int pm_runtime_put_sync(struct device *dev)
>  {
>         return __pm_runtime_idle(dev, RPM_GET_PUT);
>  }
>
> +/**
> + * pm_runtime_put_sync_suspend - Drop device usage counter and suspend if 0.
> + * @dev: Target device.
> + *
> + * Decrement the runtime PM usage counter of @dev and if it turns out to be
> + * equal to 0, carry out runtime-suspend of @dev synchronously.
> + *
> + * The possible return values of this function are the same as for
> + * pm_runtime_suspend() and the runtime PM usage counter of @dev remains
> + * decremented in all cases, even if it returns an error code.
> + */
>  static inline int pm_runtime_put_sync_suspend(struct device *dev)
>  {
>         return __pm_runtime_suspend(dev, RPM_GET_PUT);
>  }
>
> +/**
> + * pm_runtime_put_sync_autosuspend - Drop device usage counter and autosuspend if 0.
> + * @dev: Target device.
> + *
> + * Decrement the runtime PM usage counter of @dev and if it turns out to be
> + * equal to 0, set up autosuspend of @dev or suspend it synchronously (depending
> + * on whether or not autosuspend has been enabled for it).
> + *
> + * The possible return values of this function are the same as for
> + * pm_runtime_autosuspend() and the runtime PM usage counter of @dev remains
> + * decremented in all cases, even if it returns an error code.
> + */
>  static inline int pm_runtime_put_sync_autosuspend(struct device *dev)
>  {
>         return __pm_runtime_suspend(dev, RPM_GET_PUT | RPM_AUTO);
>  }
>
> +/**
> + * pm_runtime_set_active - Set runtime PM status to "active".
> + * @dev: Target device.
> + *
> + * Set the runtime PM status of @dev to %RPM_ACTIVE and ensure that dependencies
> + * of it will be taken into account.
> + *
> + * It is not valid to call this function for devices with runtime PM enabled.
> + */
>  static inline int pm_runtime_set_active(struct device *dev)
>  {
>         return __pm_runtime_set_status(dev, RPM_ACTIVE);
>  }
>
> +/**
> + * pm_runtime_set_suspended - Set runtime PM status to "active".
> + * @dev: Target device.
> + *
> + * Set the runtime PM status of @dev to %RPM_SUSPENDED and ensure that
> + * dependencies of it will be taken into account.
> + *
> + * It is not valid to call this function for devices with runtime PM enabled.
> + */
>  static inline int pm_runtime_set_suspended(struct device *dev)
>  {
>         return __pm_runtime_set_status(dev, RPM_SUSPENDED);
>  }
>
> +/**
> + * pm_runtime_disable - Disable runtime PM for a device.
> + * @dev: Target device.
> + *
> + * Prevent the runtime PM framework from working with @dev (by incrementing its
> + * "blocking" counter).
> + *
> + * For each invocation of this function for @dev there must be a matching
> + * pm_runtime_enable() call in order for runtime PM to be enabled for it.
> + */
>  static inline void pm_runtime_disable(struct device *dev)
>  {
>         __pm_runtime_disable(dev, true);
>  }
>
> +/**
> + * pm_runtime_use_autosuspend - Allow autosuspend to be used for a device.
> + * @dev: Target device.
> + *
> + * Allow the runtime PM autosuspend mechanism to be used for @dev whenever
> + * requested (or "autosuspend" will be handled as direct runtime-suspend for
> + * it).
> + */
>  static inline void pm_runtime_use_autosuspend(struct device *dev)
>  {
>         __pm_runtime_use_autosuspend(dev, true);
>  }
>
> +/**
> + * pm_runtime_dont_use_autosuspend - Prevent autosuspend from being used.
> + * @dev: Target device.
> + *
> + * Prevent the runtime PM autosuspend mechanism from being used for @dev which
> + * means that "autosuspend" will be handled as direct runtime-suspend for it
> + * going forward.
> + */
>  static inline void pm_runtime_dont_use_autosuspend(struct device *dev)
>  {
>         __pm_runtime_use_autosuspend(dev, false);
>
>
>

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